Beef heart glycogen synthase has been purified 350-fold to a specific activity of 3.0 with a recovery of 65% of the starting activity. The procedure involved isolation of the glycogen synthase-glycogen complex, alpha-amylase treatment and chromatographed on DEAE-Sepharose. The activity ratio of the enzyme activity assayed in the absence and in the presence of glucose-6-phosphate was 0.5.